From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0D12EC8C0; Mon, 15 May 2023 12:12:54 +0000 (UTC) Received: from NAM10-BN7-obe.outbound.protection.outlook.com (mail-bn7nam10on2046.outbound.protection.outlook.com [40.107.92.46]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A107D1AB; Mon, 15 May 2023 05:12:52 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=dZbzkACfo0vrr08uwcPAqfESg8dm8tUXn9bd091xAYZ8hMykx3Q9Yxr2J7MOg4QcGIvWKvGhzzWr/23nP83M0iKq/GYKMxP3ZnAd2BO3yk2wLI5sa9/nOh6dCYiUkkzWYWmVfyeo6onIVTA0KRTFAhd/vGGEUPfTheqqQ91N7avxw9hJdnXOk9n01d+e3D4Po4tzKZ+ZROLXEfb3RnXRTYDwcFRuCs3OawDI8cL215yyKZLOn1vgZzAr5iDQikAxKOgwFaCi/69wSdUmzeXrAadMcJPilTjuqo36vjlta2aS61JOrBsZ2cnWVU7/CpcIRtyBtDEc+Lx1DZ0NxJXX6g== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=vo2okyu9q4O73CTCXQvO2hUuvIL9+MVHCkrrCKsE8as=; b=C7WEr6hBBfoJRfJkl/zV8y27JXx+CpRaq5csiCtifgrb5IHxy0z6544f08OFc61vTVehtzzqLCc2D0YDqReNokxEq+ZMyHeUDci+J7icwg58mMeOmV5eTexHygpEcGcJaWc9JaoyQ8uIF0hJV6wGMHqSXiCBALaSSQ73NdHPl77A0nSCDq1iZf6o2Caabhe9swArFgBaaDJoKlVljCYXWuVS3yE3dmn1bXqKNiHl0Taf6kbF9QcetrBaHDun71Cq6s1UiQ4HLdPjADQtNDMKUwaBH6MMHQPVGFZ5J4afyyFVPIXGDeI2ipEHT4cDj7SSGyC3fmv5jPI+/k2tQK8BeQ== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=nvidia.com; dmarc=pass action=none header.from=nvidia.com; dkim=pass header.d=nvidia.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=vo2okyu9q4O73CTCXQvO2hUuvIL9+MVHCkrrCKsE8as=; b=sludTHXMA373Qn9ggvQsmqJFZB1roS03FR2loxOUAbrcy3lm60ODvyNd2TI/Z9zre4o9nUZIO5jcooarRjZvTxGKitSX1K5eN6OhEztM34W9zAPDeGTCrvUBBDhKiwZpEBrLpeomekqVUWbfNvDIVk6kXOBvcUREri7uW0zRTNN75InKTpiPkG4u04JyhrbUCuF2LLmeUs4OeFruyzt9fLIMGhs07Yy8CnTpsP1u0jvgGthlJV3oaV6pmc+ePq3bPntlyyBpyHaWNuU6SYV3mHBxjy/cz6OcRrN9oW5br9CzhvAcYtY6uC3wUsordoyssd+zzI2QR3Dxt08UaMrhTw== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from LV2PR12MB5869.namprd12.prod.outlook.com (2603:10b6:408:176::16) by BY5PR12MB4321.namprd12.prod.outlook.com (2603:10b6:a03:204::15) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.6387.30; Mon, 15 May 2023 12:12:50 +0000 Received: from LV2PR12MB5869.namprd12.prod.outlook.com ([fe80::f7a7:a561:87e9:5fab]) by LV2PR12MB5869.namprd12.prod.outlook.com ([fe80::f7a7:a561:87e9:5fab%6]) with mapi id 15.20.6387.030; Mon, 15 May 2023 12:12:50 +0000 Date: Mon, 15 May 2023 09:12:49 -0300 From: Jason Gunthorpe To: Lorenzo Stoakes Cc: "Kirill A . Shutemov" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Jens Axboe , Matthew Wilcox , Dennis Dalessandro , Leon Romanovsky , Christian Benvenuti , Nelson Escobar , Bernard Metzler , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Ian Rogers , Adrian Hunter , Bjorn Topel , Magnus Karlsson , Maciej Fijalkowski , Jonathan Lemon , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Christian Brauner , Richard Cochran , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , linux-fsdevel@vger.kernel.org, linux-perf-users@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, Oleg Nesterov , John Hubbard , Jan Kara , Pavel Begunkov , Mika Penttila , David Hildenbrand , Dave Chinner , Theodore Ts'o , Peter Xu , Matthew Rosato , "Paul E . McKenney" , Christian Borntraeger Subject: Re: [PATCH v9 0/3] mm/gup: disallow GUP writing to file-backed mappings by default Message-ID: References: <20230515110315.uqifqgqkzcrrrubv@box.shutemov.name> <7f6dbe36-88f2-468e-83c1-c97e666d8317@lucifer.local> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7f6dbe36-88f2-468e-83c1-c97e666d8317@lucifer.local> X-ClientProxiedBy: BL1PR13CA0134.namprd13.prod.outlook.com (2603:10b6:208:2bb::19) To LV2PR12MB5869.namprd12.prod.outlook.com (2603:10b6:408:176::16) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LV2PR12MB5869:EE_|BY5PR12MB4321:EE_ X-MS-Office365-Filtering-Correlation-Id: e517f40b-794c-47a4-952e-08db553db3b3 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:LV2PR12MB5869.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230028)(4636009)(346002)(376002)(39860400002)(366004)(396003)(136003)(451199021)(83380400001)(4326008)(41300700001)(6916009)(316002)(36756003)(2906002)(38100700002)(26005)(6506007)(6512007)(6486002)(478600001)(66946007)(66476007)(66556008)(2616005)(86362001)(5660300002)(8936002)(8676002)(54906003)(7366002)(7406005)(7416002)(186003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?G+qL5vFMYT6D+nnSgzfuolJgmHEgH4dPR3MTkIhI0WJ3eg35wslLv8EcGLb0?= =?us-ascii?Q?XPMpDTl5n+gVUkSBlCATUXkeEkD2tulwBCzDgo/c9CbIq9c/GuEnx7IB4Jgy?= =?us-ascii?Q?6yCBn3kJ/QuTVHb/+v23Ikknuh2l+Tjyj2T5HwufyqWM9R9VrgyeSOU9ncne?= =?us-ascii?Q?W53kCiR1qM+6BI7ehhrly4/cHMzfiasKYkkb1SJrOxNdNpAkuzSS/j/aa8VX?= =?us-ascii?Q?qsnZ3ZEktt6StW1OnQVKxB2U0MO0u/x7LoqQ0Q+0+ztFjHIMqqp/2kQqk078?= =?us-ascii?Q?4c5t7Xs8O1jcckkUhxt7fDrD4QHbXzz8k+HCnwnCe8LmObVDQAGrxJgShfQx?= =?us-ascii?Q?rhcQxMgObqXWgdt70OWPfj6MfpJUcqNYHR/FctMkNaIiPQ+0iVRsFMLBS3JZ?= =?us-ascii?Q?kGKQMAORHxn2i7qkk07xzDGmyhPKfaDGQAAfBbQSUV47IWBS3xbY6Jq0LsMb?= =?us-ascii?Q?wKAIKW7KBF8+n0qy+pXsGzl6Q6CrDmbzUS6ujjazVLnnp+puzGqCNvJKi5rW?= =?us-ascii?Q?6vij8M6UnhFHgtnIdwTysz+TsrQ8i4Ab9jsbbn1NSBSxR8uO3YWwENeYmZ+3?= =?us-ascii?Q?Sj2AheSUFe1hxa6L8uKBluXxwDDFs+CyywNnqwh/wqmgaTdf1DMtO3BBSe32?= =?us-ascii?Q?PP/uR2EbfMNIUSre12EwGxlBhYO6zdXIew5kRBKNZBH+hroIIrP93opOLQxs?= =?us-ascii?Q?Q6c2cT6mh+W0W+Nad6geqFCejguKSAwh17upFnh7KZj3+J3bHSvihjx6c2jh?= =?us-ascii?Q?Iu6VaCPqRGUsQzPII1QEuTNBF79CqgyAdhOGiYP6PZpGWoWYPBHwEufU9gsP?= =?us-ascii?Q?c9jSoFiIT85yWl4dHFzwBTDiVQn+YFsXHubFn5aLiUsHq6Tzh+0S/awPF+2E?= =?us-ascii?Q?sZv9nGYdPhx68TvqjSlBo3T0ayGbeLVO7IcY8/T6ACoFlvHFp3XzTgwRMTEO?= =?us-ascii?Q?36oCA/Ur9l8Mvc52suSFnspxgjtC/wdRwkaqyQYSiJjiQV0pfOAK6A2wRfHP?= =?us-ascii?Q?QWu16Ck3nylaL7g/A9tmXyu49JLuiw0nRfzlSVbeM0r/FcfG4/HDvXepeCs4?= =?us-ascii?Q?EuQ6xFH+hdrReNqigeBnZJTOvDNs/DEqkCIYnfWDanuae3G787aFrkTTcato?= =?us-ascii?Q?jATfBK96zi52PnqHPUT0GVuB1l9y7X5fjH4VoSHljLCe0GO4dxKRtyM/sctv?= =?us-ascii?Q?2Sim4aV4DwoX+hMoQroedjQtzpvAoYyPuYwBimAFo8YGgoxq1Bfor2qpYeGm?= =?us-ascii?Q?k2L3SrkulKiFqSRPuUeqfbc3YELxnKRCcc29Mo6ilocjjEsiAZX0F9rCqGkZ?= =?us-ascii?Q?bKJaY33kmJQCcQ5zsY8bQAgbfGBF61NlDpaGUjQhV53tYJpN0axpZhlDnkTK?= =?us-ascii?Q?hLfJgkPqzyzZ2kh5bMRpRHv1lJM88A8CrVjld9HYuq/xCZ//OcWQeAnGiNdL?= =?us-ascii?Q?g9AqsFxbEkFIoECXTR3j8GsWlWbT4V6EsS1B5nj3uqJvdvzHi09DV4PTbfIU?= =?us-ascii?Q?fdwpnItvvGh+ETUOJk9ljuhbyxc4ELMLBBnqvZVStZ0iEpTDmZ1WeiJe6Vz2?= =?us-ascii?Q?HkXq9o4Id3e9FyX79yFP2boAC4P5tgeLP9a4BWz8?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: e517f40b-794c-47a4-952e-08db553db3b3 X-MS-Exchange-CrossTenant-AuthSource: LV2PR12MB5869.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 May 2023 12:12:50.0813 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 8quOnnNBOxdw4tqchzoE4R9DYph0firWZ099EtdbNRWYDxYS5r2wSK5qv1YCcYK0 X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY5PR12MB4321 X-Spam-Status: No, score=-1.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FORGED_SPF_HELO, RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_PASS,SPF_NONE, T_SCC_BODY_TEXT_LINE autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net On Mon, May 15, 2023 at 12:16:21PM +0100, Lorenzo Stoakes wrote: > > One thing that came to mind is KVM with "qemu -object memory-backend-file,share=on..." > > It is mostly used for pmem emulation. > > > > Do we have plan B? > > Yes, we can make it opt-in or opt-out via a FOLL_FLAG. This would be easy > to implement in the event of any issues arising. I'm becoming less keen on the idea of a per-subsystem opt out. I think we should make a kernel wide opt out. I like the idea of using lower lockdown levels. Lots of things become unavaiable in the uAPI when the lockdown level increases already. > Jason will have some thoughts on this I'm sure. I guess the key question > here is - is it actually feasible for this to work at all? Once we > establish that, the rest are details :) Surely it is, but like Ted said, the FS folks are not interested and they are at least half the solution.. The FS also has to actively not write out the page while it cannot be write protected unless it copies the data to a stable page. The block stack needs the source data to be stable to do checksum/parity/etc stuff. It is a complicated subject. Jason